Every ham has a favourite "first", a first receiver, a first
contact, a first good key, first DX contact, etc, and for me
there is a first construction project. This one inspired me
to get into ham radio. While i never did actually build it as
a first transmitter ( that one came in 1976, and turned out to
be a 2 stage MOPA with a transformer power supply and a 6L6
final at 20 watts) it did introduce me to the idea that
building equipment could be done at a simple level with parts
readily available, and on a shoe-string budget at that. This
project showed me that a ham ticket would be worthwhile to get
if i could build these neat things and talk all around the State.
You see, i was a CBer in 1968, and it cost me $120.00 just to
talk 30 miles. CW or not, if i could build something for a lot
less and communicate a lot farther, why stay with CB??

I then resolved that i would become an Amateur Radio Operator,
and further, build all of my equipment. As time and re-locations
occured ( my dad was a career military intelligence specialist
and we lived several years in Germany ), i finally realised my goal
the winter of 1976 - 77. Although i wound up making another
transmitter entirely, i kept this article in my library, just
the clipping, to remind and challenge me, to keep the fires of
motivation burning.

Sometime in the early nineties, CQ magazine ran a series of
"Classic Homebrew" articles in the "World of Ideas" section
authored by David Ingram, whom i had met at the Atlanta Hamfest
in 1991 (i love to drop names. Makes me feel so . . . so . . .
. . . important.) W5LETs article was mentioned, so i figured,
heck, i still have that old article stashed away, why not give
it some air time as a classic of a classic on the web?

So, folks, as a tip o' th' hat to both Mr. White and Mr. Ingram,
here it is, an re-edited version of the classic Tri-Tet one-tube
Crystal killer. Read it for fun, or just go ahead and make
one: hey, no transformer, which costs as much as the rig itself
these days (although, in my cushy little safety coccoon, i would
advocate a nice, beefy isolation transformer at least, to distance
the builder some from ground. Or, a nice variac.)

Just . . . . beware of Lethal Voltages. Gotta warn you about that.
It's kinda sad, when you think about it, Boy Scouts have built these
things for years to earn Merit Badges, and they had enough common
sense to already know that. But these days of recounting dimpled
chads and folks not following simple instructions, ya gotta make
it REAL PLAIN : DO NOT, I REPEAT, DO NOT INSERT THE 117 VOLT LINE
PLUG INTO YOUR EYE, MOUTH, OR OTHER BODY PARTS !!! DO NOT PLACE
THE 50C5 TUBE INTO YOUR MOUTH AND BITE DOWN HARD !!!! DO NOT INSERT
YOUR TONGUE AT OR NEAR THE OUTPUT OF THE FILTER CAPS !!! Sheeesh !!
Now that y'all have been warned, enjoy.

A Word about the Schematics and the Drawings: These are
re-drawn from the original article. TubePad is used for both.
TubePad 5.0 is available from my Website as a free download,
just follow the link on the main page or click
here.

The Bare Essentials Transmitter (mostly transcribed directly from the
original text of the article.)

Everybody talks about inflation these days. According to the experts,
we're spending too much and driving the price of everything sky high.
Washington now threatens us with higher taxes to stop our spree.
( Note: remember, this is written in the pre-Greenspan era, Johnson was
still the President !) But for hams on a budget there's a way to have
your cake and fight inflation, too. You do spend a little of the green
stuff but it won't make much of a dent in your wallet or the national
economy. The way out: our Bare-Essentials Transmitter. This little 40
and 80 meter rig takes the prize as the anti-inflationary CW transmitter
of the year (1968). You spend only $ 7.00 to get it on the air. There's
no chassis. The rig is built on a piece of wood ---- any kind, like the
end of an orange crate, will do. And for tie points you use finishing
nails. The 50C5 (or a 50L6) tube can be salvaged from an old AC/DC radio.
You'll have to spend 11 cents (Jeeepers!) for a tube socket but you won't
have to buy a socked for the crystal. It's not fancy but it packs a wallop
for its price. Used with a mediocre antenna, it has worked stations all over
the U.S. When conditions are right and with a good antenna there is no reason
why it can't work some real DX.

The transmitter consists of a 50C5 crystal oscillator, which operates on either
40 or 80 meters. Since the 50C5 has a 50-V filament, it uses a 400 ohm 20 watt
dropping resistor instead of a filament transformer. The power supply for the
plate and screen voltages is a doubler which provides about 350 VDC. Two capacitors,
two silicon rectifiers and a 1- watt resistor complete the power supply.

First thing is the chassis, which is simply a 10 x 6 x 3/4 inch thick piece
of wood. Take a close look at the pictorial to see where each part goes.
The tube socket is mounted on short spacers so that its lugs clear the wood.
(gary's note: the xtal seems to be attached by alligator clips soldered to mounting
nails -- i would, however, use a socket of some type, if available, as i show
in the re-drawn pictorial.)
The rest of the parts are soldered to finishing nails in the board.
(Note: i would encourage soldering spade lugs on the end of the wires and
using screws instead of nails as an alternative. This provides somewhat more
of a finished look to the construction. Also, consider the use of tempered
clip-board masonite on a wood frame, to facilitate some underwiring as well.)
The power supply components are located in the upper right corner of the board.
There is no power switch so the AC leads go directly to the nails (or screws).
Nails ( or screws ) again are used for connecting points for the antenna and
for the key. Another nail, located at the lower right of the board is for the
ground connection for neon lamp-NL1. If the AC plug is in the wrong way, the
hot side of the line will be connected to the key. This will mean that 117v
exists from the key to ground, ENOUGH TO CAUSE SEVERE SHOCK. However, if the
plug is reversed, the ground side of the AC line will be connected to the key
circuit and a shock hazard will not exist. (gary's note: on open breadboard
circuitry such as this, the term "shock hazard" is relative. There is ALWAYS
a hazard if one is not careful, so be careful, OK??)
By connecting a water-pipe ground to the nail, the neon lamp will light if
the AC plug is in the wrong way. (so, view the neon light as a WARNING light.)
Observe carefully the polarity of the silicon rectifiers and the electrolytics.
The coils are wound on plastic pill bottles. The 80 meter coil is wound on a
1-1/2 inch diameter by 3-1/2 inch long bottle. The 40 meter coil is wound on
a 1-3/16 or 1-1/4 inch diameter by 2 inch long bottle. First drill a small hole
in the bottom of each of the bottles for the mounting screw.
The plate winding (primary) for the 80 meter coil is 45 turns of #24 enameled
wire, closewound. The 40 meter primary is 23 turns of #24 enameled wire also
closewound. Both secondaries are #20 solid hookup wire : the 80 meter is four
turns, the 40 meter three turns.
Before winding the primaries drill four small holes (two at the top and two at
the bottom of the primary winding) in each form. Then thread the ends of the
primary wire through these holes.
The secondaries are wound over the primary coils and are held in place by
twisting the ends together.

At this point, this is where I deviate from the printed text.
There are some things I would endeavour to point out. 1- This project uses a
compression cap for tank tuning, which, I suppose, isn't too bad, and is
definately cheaper than a standard air variable, but i would use the latter
as a precaution. Also I would provide some provision to tune the antenna coil,
even if it is simply proximity tuning by sliding the coil. Because there is
exposed wiring, be very cautious tuning the compression cap because of the
high voltages exposed and open. Dropping a screwdriver could result in some
interesting fireworks and aroma. This is why I advocate the use of Masonite
and underwiring when at all possible. One method of tuning this kind of rig
comes down from the old Novice Class crowd who spent all their money just
gettin the receiver and decent key and couldn't afford a milliamp meter:
Take a No. 47 bulb, and solder to it one or two loops of wire the diameter of
which matches that of the output tank coil. This serves as an absorbtion device.
Next, attach the coax connected to a resonant dipole ( one which has a known
feedpoint impedance of about 50 - 75 ohms ). With the light-bulb coil coupled
closely to the tank primary, rotate C4 till the bulb starts to glow. Slowly
adjust C4 to maximum brightness. This proceedure can be done with a 50 ohm 20
watt resistor serving as the load, and then replacing the resistor with the
transmission line when the output tank is tuned to maximum brightness of the
"Absorbtion indicator" assuming the antenna impedance is similar to the load
resistor used. Still another, maybe simpler way is to connect a 5 watt
lightbulb to the antenna output coil, and tune C4 to maximum brightness.
Then connect the transmission line. If you have a 0 - 100 mA meter, just connect
it in the B+ line, bypassing RF around it with a couple .01uF caps, and tune for
minimum current. If you have an SWR meter,
you can read the forward power and slide the antenna coil back or forward to a
point where maximum forward current is indicated, then re-dip C4 to minimum
current on the mA meter. ( the good ol' peak and dip method.)

This little rig should realise about 5 watts input, 2 watts out. You might have
to experiment some with the best type of transmission line and antenna. An antenna
tuner might come in handy.
Return to top